1. Field of the Invention
This invention relates to apparatus for sampling fluids from a formation reservoir in a well, and more particularly, to a sampling apparatus having a large sampling chamber therein and at least one modular sampling means disposed in the sampling chamber adapted for separately entrapping a volume of fluid as the sampling chamber fills.
2. Description of the Prior Art
It is frequently necessary to obtain information about fluid in a well formation reservoir prior to actually producing the well. Measuring the pressure and temperatures of the fluid is important, but it is also desirable to obtain an actual sample of the fluid and bring that sample to the surface so that the physical characteristics of the fluid may be observed. As a result, numerous testing and sampling apparatus have been developed.
One such formation tester is disclosed in U.S. Pat. No. 216,559 to Halliburton, assigned to the assignee of the present invention. This apparatus includes a packer with perforating guns positioned therebelow and having a valve therein such that after the packer is set and the guns triggered, fluid from the well formation reservoir flows through the valve into a cylindrical body at the lower end of the tool string. When the drill string is raised, the valve recloses such that a volume of fluid is contained in the lower portion of the drill string. The drill string may be removed from the well bore and the sample drained for testing.
One problem with this apparatus and other sampling apparatus previously known is that hydrocarbons from the well formation are actually flowed into the tool string or to the surface. Because the formation is at a relatively high pressure, there is always a danger of a blowout of the well. Also, if sour gas is present in the sample fluid, special equipment is necessary on the surface and downhole for handling it.
The present invention solves these problems by providing a tool with a totally enclosed sampling chamber such that the hydrocarbons from the well formation reservoir are never flowed into the tool string and never flowed above the packer. Because the fluid sample is totally enclosed, the sampler may be handled at the surface, and a minimum of special equipment is needed for handling the fluids in the sampler even if the sample fluid contains sour gas.
Samplers adapted for obtaining a self-contained sample have been used on wire lines. In such apparatus, the tool is lowered on a wire line and perforating guns triggered and the sample chamber filled. Because the device is used on a wire line, it is not possible for a large fluid sample to be obtained. The present apparatus which is lowered on a tool string obviously has no such weight limitations. Also, wire line sampling devices are not totally reliable and frequently the sample obtained is less than desirable.
Another problem with such previously known sampling apparatus is that a single fluid sample is obtained. The present apparatus which utilizes a separate sampling module positioned in the main sampling chamber provides an easily portable sample which may be individually tested in a laboratory. In particular, a plurality of longitudinally spaced sampling modules may be used along with pressure and temperature gauges to obtain more complete information about the fluid in the formation reservoir.
An additional difficulty with previously known sampling apparatus is that it has been hard or impossible to know when the sampler had actually opened and closed. The modular sampling means of the present invention utilizes metering means for allowing a predetermined volume of fluid to enter a sampler module chamber prior to automatically closing metering valve means therein.